1. Field of the Invention
The present invention relates to a calibration method, and some preferred embodiments relate to a method of calibrating an optical axis of a sensor mounted on a robot hand to teach a position of a semiconductor wafer to a semiconductor wafer carrying robot.
2. Description of Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
Conventionally, teaching operation of a semiconductor wafer carrying robot is performed such that an operator guides the robot by confirming the position of the wafer to be carried while visually observing the wafer in the same manner as in a common industrial robot. In some cases, however, it is very difficult or impossible to visually observe a wafer in a processing apparatus or the like from the outside. In view of the above, there are some proposed methods/apparatuses called “auto teaching methods/apparatuses” in which a teaching tool having the same size as an actual wafer is disposed in a processing apparatus in place of a wafer and the position of the teaching tool is detected by a sensor installed on a robot's end effector to teach the position to the robot.
The inventors of this invention proposed a method of sensing a teaching tool using a hand equipped with two permeation type sensors (see WO 2003/22534, hereinafter referred to as “Patent Document 1”). In this method, the hand is approached to a small circular disc provided at a teaching tool from different directions to obtain the teaching position of the robot, i.e., R, θ and Z values of the cylindrical coordinate system (R-θ-Z) by applying a least-squares method to the results. Here, the R value denotes the teaching value of the robot arm in the expansion/contraction direction, the θ value denotes the teaching value of the robot in the rotation direction, and the Z value denotes the teaching value of the robot in the up-and-down direction.
On the premise of performing the so-called automatic teaching, it is required that the optical axis of the sensor on the hand is adjusted correctly. However, the aforementioned reference fails to disclose any means for adjusting the optical axis. Furthermore, although the misalignment of the setting angle of the hand itself will also be added as misalignment of the optical axis, no method of correcting the setting angle by obtaining the misalignment of the optical axis correctly has been proposed.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.